The present invention relates generally to tea and, in particular, to a process for making from tea leaves a water soluble product, for example, an extract, concentrate or powder, which is capable of being reconstituted to a tea beverage substantially free of undesirable cloudiness and/or turbidity.
The processing of leaf tea to form a water soluble extract, concentrate or powder which will reconstitute to a tea beverage is, in its general aspects, well known in the art. Thus for example, green or black (fermented) leaf tea is typically extracted with hot water to form a dilute extract containing soluble tea solids. The insoluble leaf material is discarded and the extract is then concentrated to form a concentrated extract which may be sold as is (for example, in frozen, refrigerated or otherwise preserved condition) or dried in an appropriate manner to form a shelf-stable powder.
In the preparation of soluble tea products intended to be reconstituted in cold water and/or consumed cold, much attention has been directed to the elimination of the turbidity or cloudiness which often manifests in the reconstituted beverage. To this end, a wide variety of processes have been proposed to effect the elimination of the cold-water insoluble materials which cause such cloudiness. For example, it has been proposed to employ chemical or enzymatic agents to solubilize the insoluble components; to remove the cold-water insoluble materials or their precursors; or to extract the tea leaf in a manner such that the insoluble materials contributing to or resulting in cloudiness are not leached from the leaf.
The preparation of soluble tea products for reconstitution and consumption in warm or hot water is not generally attended with the difficulties noted with respect to cloudiness and turbidity. Hence, with the exception of a preliminary clarification of the dilute extract resulting from the hot water extraction of tea leaf to remove extraneous undissolved solid portions of the tea or other extraneous materials, it has not been found necessary in commercial processing to conduct elaborate chemical and/or mechanical operations aimed at removing or repressing components which result in cloudiness.
In view of the foregoing, our experience with the processing of both fermented and green Soviet (Georgian S.S.R.) tea to form hot or warm-water reconstitutable tea concentrates and powde was surprising in finding that application of standard processing operations (i.e., extraction, concentration and drying) to this starting tea leaf material resulted in reconstituted beverages which displayed considerable cloudiness and turbidity. Further investigations showed that the dilute extract obtained from extraction of the tea leaf, when clarified, itself showed no turbidity or cloudiness upon dilution with warm water to beverage strength. However, beverages prepared by reconstituting powders obtained by direct spray- or freeze-drying of this dilute, clarified extract displayed excessive cloudiness. The same result appeared in products prepared by reconstituting extracts obtained by concentrating the dilute, clarified extract, and it was noted in these tests that the solids which caused the undesirable cloudiness in the beverage were generated in situ during the concentration process. However, it proved in further testing to be impractical to physically remove the solids from the concentrated extract once they were formed.
As a result of our studies it became apparent that a process other than those typically employed or proposed in removing from tea extracts insoluble or suspended particles and components contributing to cloudiness in the final beverage would have to be developed, since the actual insolubles were present, not after extraction of the tea leaf, but only after in situ formation during further processing of the extract obtained from the leaf.